Regulation by proportionate pressure and apparatus therefor



Oct. 2, 1928.

1,685,787 c. H. SMQOT REGULATION BY PROPORTIONA'IE PRESSURE AND APPARATUS THEREFOR Filed Dec. 16, 1926 wmm/ Patented Oct. 2, 1928. 2

6 UNITED STATES CHARLES E. SHOOT, OF MAPLEWOOD, NE'N REGULATION BY PROPORTIONATE PRESSURE AND APPARATUS THEREFOR.

Application filed December 16,1926 Serial No. 155,281.

My invention relates to the art of regulation by'pressure and more specifically to the art of furnace regulation by proportionate pressures.

One purpose of my invention is to provide apparatus for regulating the draftin a furnace to insure an efficient and also a thorough.- ly safe working pressure above the fuelbed.

Another purpose of my invention is to provide means whereby a negative pressure, that is, one below that of the atmosphere, may be automatically roportioned to a positive ressure or one a ove that of the atmosp iere, whether for the purpose of furnace regulation or for any other purpose.

Still another urpose of my invention is to provide means or maintaining constant the average of two pressures.

Other objects and features of novelty will become apparent from the accompanying description and the claims annexed thereto.

I will describe my invention as applied to the re ulation of aboiler plantor furnace, al-

though it will be apparent that its appliestion is not limited thereto but may be used wherever it is desired to regulate by pressure.

For correct draft regulation in a furnace there are two conditions that must be fulfilled, namely, safety and eficiency in combustion. For safety the pressure above the fuel bed in a furnace must not be greater than that of the atmosphere to prevent possible blowouts and scorching of the walls of the furnace; for efficiency in combustion this pressure must be maintained as close to atmospheric as is consistent with the requirement for safety, to prevent the sucking m of cold air through the walls of the furnace. The dangers of sudden increase of pressure within the furnace are due to causes within the fuel bed. When the fuel bed is thin or uneven, irrespective of the rating or load, danger of blowouts is im minent. When forany reason the fuel bed is thin or uneven, the average pressure within the bed will tendto rise, and 1f the draft is so controlled as tov effectively counteract this tendency then there will always be a ressure above the fuel bed that is safe, and t at is no further from the ideal atmospheric pressure than the immediate conditions demand.

I, therefore, have devised means for regulating the draft in response to the difierential between the average pressure within the fuel bed and that of the atmosphere which results in maintaining approximately constant atmospheric pressure within the bed. With this pressure held'atmospheric or close to it, the

pressure above the bed can never be dangerous nor will it be far from that desired for efficienc-y. Regulation by this method ,is, therefore, thoroughly safe and at the same time more eflicient than those which vary the furnace pressure proportionately with the rating or load. In devising apparatus to maintainthe pressurewithin the fuel bed at that'of the atmosphere, I have avoided any necessity for introducing a conduit to any point within the bed itself, as it is obvious that this would be a very difiicult, if not impossible, procedure, and the pressure at any definite point or points within the bed would not necessarily correspond to the average of that within the whole bed.

For anunderstanding of my invention and.

-- link 7', rod 8 and lever 9 with the piston rod 10 of the regulator 11, hereinafter to be described. A chamber 12 of the regulator is connected by means of the conduit 13 to the conduit 14 having the branches 15 and 16. The branches 15 and 16 are provided with the adjustable reducing valves 17 and 18 respectively and terminate at points 19 and 20 within the furnace and below and above the furnace through the inlet 3 from the blower 21 and regulated by the damper 6, which, as shown, is operated by hand. The operation of the damper 6 is immaterial to my fuel bed respectively. Air is supplied to the present invention and might be controlled automatically by the steam pressure or in any other well known manner, as desired. The.

regulator 11 illustrates my preferred means for controlling the damper 5in response to the differential between the pressure within the conduit 13 and that of the atmosphere. I

The operation of this regulator will be only briefly described, as it forms no part of my present invention. It is sufficient for my present purpose to state that air at atmospheric pressure enters the chamber ,22 through an opening 23 and acts upon 'the diaphragm 24 to oppose the; pressure in the chamber 12, a difference in, these pressures causing a movement of the diaphragm. and

of the rod which is attached through intermediate rigid members to the diaphragm and which controls a leakage port 26. This leakage port in turn controls the flow of an auxiliary fluid at high pressure and causes the pressure of this fluid to move the piston 27 and the rod so as to operate the damper 5 through the lever 9, rod 8 and link 7, a lowering of the rod 11 tending to close the valve 26 and resulting in a rise of the piston 27 with consequent opening of the damper 5. The auxiliary fluid which may be oil or steam, for example, enters the regulator through the pipe 28 and flows out through the pipe 29.

The regulator 11 thus tends to change the posit-ion of the damper 5 whenever the pressure within the conduit 13 varies from that of ,the atmosphere.

It will be shown, furthermore, that the movement of the damper isin such a direction as to return the pressure within the conduit 18 to that of the atmosphere. The regulator therefore could be replaced by any means for controlling the damper in response to the differential between the pressure of the atmosphere and that within the conduit 13. The apparatus operates to proportion the negative pressure above the bed to the positive pressure below the bed and to maintain atmospheric pressure within the fuel bed 2 according to the following theory. a 1

During combustion there will be a flow of air and gases through the furnace and a consequent drop in pressure from inlet to exhaust. The conduit 14 permits a bypath flow from the point of higher pressure 19 below the fuel bed to that of lower pressure 20 above the bed, which flow, for any given position of the valves 17 and 18, will bear a definite relation to the flow through the fuel bed between the same points 19 and 20. The cross-sectional area of the conduit 14 is preferably made small enough to insure that the volume of air by-passed around the fuel bed will be practically negligible compared to the mainair flow through the furnace. There will be -a-static pressure in the conduit 13, such pressure depending upon the relative resistance offered by the branches 15 and 16 to the bypath flow and upon the static pressures at points 19 and 20. It is obvious that the pressure in the conduit'13 will be equal to that at some point within the furnace be- .pressur'e within the fuel bed. If this aver-- age pressure within the fuel bed, and therefore the pressure within 1.3, is greater than atmospheric, the damper 5 will be opened sufliciently to suck out more gas and thereby reduce this'pressure to atmospheric. S1m1- larly if this pressure is lessthan atmospheric the damper tends to close until :he pressure within the fuel bed, and therefore that with the conduit 13, builds up to that of the atmosphere. In order to obtain a pressure in the conduit 13 equal to the average fuel bed pressure, the apparatus might theoretically be constructed without valves 17 and 18, but the provision'o't valves 17 and 18 makes exact construction unnecessary as they provide means to vary the resistance in either one of the branches l5 and 16 and so adjust the pressure in conduit 13 to-correspondto the average fuel bed pressure. Moreover they also enable the pressure in conduit 13 to be adjusted if desired to that at. any other point within the furnace between the points 19 and 20. A slight closure of the valve 17 with the valve 18 left open increases the resistance to flow of the branch 15 relative to the branch 16, and thereby reduces the pressure in conduit 13 until it is equal to that at a point in the furnace nearer to the point 20 than to 19, and results in proportionately small increases in negative pressure at 20 in response to large increases in positive pressure at 19.

Similarly a partial closure of the valve 18,

the average of that within the fuel bed. No

further adjustment is required so long as it is desired to regulate by the pressure withm the fuel bed. It is obvious, however, that under special conditions of operation it might be desired to regulate by the pressure at some point above or below the bed, in which case the valves 17 and 18 supply a ready means for readjusting the pressure in the conduit 13 to correspond to the pressure at the point by which it is now desired to regulate.

' It is not essential to my invention that the exhaust damper be the draft controlling means. It is obvious that an exhaust fan could be used for thispurpose, the speed of which would be responsive to variations in pressure within the conduit 13. Or, instead of the exhaust damper or fan, the inlet a1r supply, either bydamper or fan, could be controlled in response to this pressure with the exhaust damper or fan controlled in any desired manner.v It is only necessary in so far as this part of my invention is concerned that the fuel bed pressure be maintained substantially atmospher c in response to the differential-between the pressure in the conduit 13 and that of the atmosphere.

I have now described my new apparatus for regulating the draft in a furnace. It is apparent that the apparatus disclosed is not limited to the precise use here shown but may.

' the mainllow and one, thereform which does not appreciably allect the maiirilow.

I claim:

1. In systems for regulationby pressure, a pressure responsive device, anjapparfatus for obtaining a' press'ure corresponding to that at a point within a flow of fiuid which co n-.

sists in a bypass for permitting a bv-path flow from points before topoin ts beyond said first mentioned point, means for transmittin the pressure at a point (along said by-patli flow to said device and'means for ad usting the resistance fto flow of parts of said by-pass.

2. In systems for regulation by fluid pres-v sure, means for maintainin constant the average oftwo variable fluid-pressures, between which-there is a flow of fluid, comprising in 'combination' ia flow regulator, means for, creating a pressure corresponding to the average of saidflv'ariable pressures, a

device responsive to a constant pressure and said created pressure, and means for controlling said regulator by said device.

' 3. In a furnace having a fuel bed and a draft regulator, a conduit by-passing said bed to connect points of positive pressure be low said bed with points of negative pressure above said bed, a device for controlling said regulator including two chambers, a conduit connecting one of said chambers with said first nientloned conduit, and a connection to the atmosphere from the other of said chambers.

4. Apparatus as in claim 3 wherein said first mentioned conduit is provided with two throttling valves and where the connection between said conduits is intermediate said valves.

5. in systems for regulation by fluid pressure, means for maintaining constant a pressure intermediate two. variable fluid pressures between which there is a flow' of fluid, con'iprising in combination a flow regulator, means for creating a pressure corresponding to said intermediate pressure, a device responsive to a constant pressure and to said created pressure, and means for controlling said regulator by said device.

In testimony whereof, I have signed my name to this specification.

CHARLES H. SMOO'R; 

